Photo-Physical Properties of Simple and Double Strand Multi-Porphyrinic Polypeptides

One of our research field concerns porphyrin-functionalized a-polypeptides to control the spatial organization of the chromophores and enable exciton migration through the pool of porphyrins to mimic the light harvesting antennae of the photosynthetic system.¹

      In the photosynthetic system, the solar energy is collected by pigment molecules attached to the light harvesting complexes, in which the chlorophylls are held in a parallel orientation by fairly short a-helical polypeptides. When a photon hits one of the chlorophylls, the absorbed energy spreads extremely rapidly to the others until the reaction center is reached.¹ Succeeding in organizing the porphyrins in a similar way as nature does should provide information about the relation existing between the orientation of the chlorophylls and the efficiency of nature in transferring an excited state over a very long distance and with minimal loss of energy.

The right-handed 3₁₀ helical conformation adopted by our poly-L-lysine functionalized with eight porphyrins induces an overlap of the chromophores, which thus present sufficient electronic coupling to promote a good exciton migration within the molecular wire. We thus synthesized a good model of the light harvesting antennas of the photosynthetic system (studies realized in collaboration with Prof. T. Keiderling, University of Chicago, US and Prof. T. Majima, SANKEN, Osaka, Japan).²

      Our peptides with pendant porphyrins were studied extensively throughout the world in collaboration with foreign colleagues, and found applications as organic photovoltaic cells,³ or redox molecular switches⁴ (studies realized in collaboration with Prof. S. Fukuzumi, Univeristy of Osaka, Japan and Dr. P. Ceroni, University of Bologna, Italy).

These polypeptides with pendant porphyrins also found applications for the successful purification of Single-Walled Carbon Nanotubes (studies realized in collaboration with Prof. S. Fukuzumi, Univeristy of Osaka, Japan).⁵

 

 

Acknowledgements

This work was supported by the CNRS and the French Ministry of Research. 

References

1. W. Kühlbrandt, Nature 1995, 374, 497-498.
2. M. Fujitsuka, D. W. Cho, N. Solladié, V. Troiani, H. Qiu, T. Majima, J. Photochem. Photobiol. A 2007, 188, 346-350. 
3. T. Hasobe, K. Saito, P. V. Kamat, V. Troiani, H. Qiu, N. Solladié, K. S. Kim, J. K. Park, D. Kim, F. D'Souza, S. Fukuzumi, J. Mater. Chem. 2007, 39, 4160-4170.
4. Paola Ceroni, Giacomo Bergamini, Nicolas Aubert, Vincent Troiani, Nathalie Solladié, Chem. Phys. Chem. 2005, 6, 2120-2128.
5. Kenji Saito, Vincent Troiani, Hongjin Qiu, Nathalie Solladié, Takao Sakata, Hirotaro Mori, Mitsuo Ohama,  Shunichi Fukuzumi, J. Phys. Chem. C  2007, 111, 1194-1199.